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Odd Man Out and Series – Missing No.

Insert the missing number.
1. 16, 33, 65, 131, 261, (….)
A. 523
B. 521
C. 613
D. 721

Answer: Option A

Explanation:

Each number is twice the preceding one with 1 added or subtracted alternatively.

So, the next number is (2 x 261 + 1) = 523.


2. 10, 5, 13, 10, 16, 20, 19, (….)
A. 22
B. 40
C. 38
D. 23

Answer: Option B

Explanation:

There are two series (10, 13, 16, 19) and (5, 10, 20, 40), one increasing by 3 and the other multiplied by 2.

3. 1, 4, 9, 16, 25, 36, 49, (….)
A. 54
B. 56
C. 64
D. 81

Answer: Option C

Explanation:

Numbers are 12, 22, 32, 42, 52, 62, 72.

So, the next number is 82 = 64.


4. 2, 4, 12, 48, 240, (….)
A. 960
B. 1440
C. 1080
D. 1920

Answer: Option B

Explanation:

Go on multiplying the given numbers by 2, 3, 4, 5, 6.

So, the correct next number is 1440.


5. 8, 7, 11, 12, 14, 17, 17, 22, (….)
A. 27
B. 20
C. 22
D. 24

Answer: Option B

Explanation:

There are two series (8, 11, 14, 17, 20) and (7, 12, 17, 22) increasing by 3 and 5 respectively.

6. 11, 13, 17, 19, 23, 29, 31, 37, 41, (….)
A. 43
B. 47
C. 53
D. 51

Answer: Option A

Explanation:

Numbers are all primes. The next prime is 43.
7. 8, 24, 12, 36, 18, 54, (….)
A. 27
B. 108
C. 68
D. 72

Answer: Option A

Explanation:

Numbers are alternatively multiplied by 3 and divided by 2.

So, the next number = 54 ÷ 2 = 27.

8. 2, 6, 12, 20, 30, 42, 56, (….)
A. 61
B. 64
C. 72
D. 70

Answer: Option C

Explanation:

The pattern is 1 x 2, 2 x 3, 3 x 4, 4 x 5, 5 x 6, 6 x 7, 7 x 8.

So, the next number is 8 x 9 = 72.

9. 4, -8, 16, -32, 64, (….)
A. 128
B. -128
C. 192
D. -192

Answer: Option B

Explanation:

Each number is the proceeding number multiplied by -2.

So, the required number is -128.

10. 7, 26, 63, 124, 215, 342, (….)
A. 481
B. 511
C. 391
D. 421

Answer: Option B

Explanation:

Numbers are (23 – 1), (33 – 1), (43 – 1), (53 – 1), (63 – 1), (73 – 1) etc.

So, the next number is (83 – 1) = (512 – 1) = 511.

11. 5, 10, 13, 26, 29, 58, 61, (….)
A. 122
B. 64
C. 125
D. 128

Answer: Option A

Explanation:

Numbers are alternatively multiplied by 2 and increased by 3.

So, the missing number = 61 x 2 = 122.

12. 15, 31, 63, 127, 255, (….)
A. 513
B. 511
C. 517
D. 523

Answer: Option B

Explanation:

Each number is double the preceding one plus 1.

So, the next number is (255 x 2) + 1 = 511.

13. 1, 8, 27, 64, 125, 216, (….)
A. 354
B. 343
C. 392
D. 245

Answer: Option B

Explanation:

Numbers are 13, 23, 33, 43, 53, 63.

So, the missing number is 73 = 343.

14. 3, 7, 6, 5, 9, 3, 12, 1, 15, (….)
A. 18
B. 13
C. -1
D. 3

Answer: Option C

Explanation:

There are two series, beginning respectively with 3 and 7. In one 3 is added and in another 2 is subtracted.

The next number is 1 – 2 = -1.

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